1. Field of the Invention
The present invention relates to a velocity calculating device which is capable of estimating momentary velocity of a vehicle precisely when it collides and a hood raising system which is capable of raising a hood of the vehicle on the basis of the momentary velocity thereby to protect an object from being damaged.
2. Description of Related Art
A conventional hood raising system operates as follows. When the vehicle on traveling collides against the object, then the system detects the collision by a touch sensor and simultaneously operates to raise a hood arranged on the front side of the vehicle to prevent the object from colliding with rigid components, such as an engine, through the intermediary of the hood, thereby protecting the object.
In the above hood raising system, a velocity calculating device calculates an average velocity at intervals of predetermined times as a standard on the basis of velocity pulse signals generated from a vehicle velocity sensor. Also, the system is so constructed as to raise the hood when the so-calculated average velocity is within a predetermined range as a standard, thereby distinguishing from normal collisions.